The present invention relates to a device for coupling together in leaktight manner two smooth tubes disposed end-to-end and of substantially the same diameter.
French Patent No. 2 662 486 discloses a device of that type which comprises a sleeve suitable for being disposed around the facing ends of the two tubes, which sleeve is provided with means for reducing its diameter under the action of tightening means. That device further comprises a sealing ring suitable for being a disposed inside the sleeve so as to surround the facing ends of the two tubes, said ring being constituted by a looped flat strip having first and second longitudinal ends suitable for coming into contact with each other when, with the ring being situated inside the sleeve, said sleeve is tightened around the facing ends of the tubes.
For example, the sleeve has two free ends provided with assembly lips which define an axial slot between them. The assembly lips are suitable for co-operating with means for tightening the sleeve, which means are suitable for bringing the lips towards each other so as to reduce the diameter of the sleeve.
Devices of that type serve in particular to interconnect two exhaust tubes. The requirements as regards the leaktightness of the fitting are increasingly stringent. It might be thought that the more the sleeve is tightened onto the tubes, the more the leaktightness is improved. Indeed, it is true that one of the conditions required to obtain leaktightness is that the inside periphery of the ring must be in leaktight contact with the outside peripheries of the tubes. However, the more the sleeve is tightened, the more the diameter of the sealing ring is reduced. Thus, in order to obtain leaktightness in the region of the join between the longitudinal ends of the ring, it is necessary for said ends to be in leaktight contact as of a given degree of tightening and, in addition, for further tightening of the sleeve once said contact is established not to degrade the leaktightness, e.g. by causing the two longitudinal ends to overlap.
To that end, French Patent No. 2 662 486 proposes a ring whose longitudinal ends are bevelled so that they can be applied one against the other and be shifted transversely relative to each other as the diameter of the ring decreases. That solution is generally satisfactory because it makes it possible to avoid overlapping on tightening, even if such tightening is excessive. Unfortunately, it does not make it possible to have full control over the extent to which the two free ends press against each other, so that that pressing together might not be sufficient for the contact to be leaktight. In addition, by enabling the ends of the ring to shift transversely relative to each other, it does not make it possible for the ring to be set inside the sleeve.
French Patent Application No. 2 748 542 offers another solution consisting in providing the sealing ring with a capacity to deform so that its length is decreased when the free edges of said ring are urged into abutment against each other. For that purpose, that patent application recommends providing perforations in the vicinity of one of the edges of the ring.
That device is satisfactory and gives excellent results in particular when the sealing ring is made of a soft material such as aluminum. For other materials, in particular for aluminum-coated steel, the deformable nature of the free edges of the ring is more difficult to control, and the manufacturing costs reflect that.
Patent US 1 978 195 shows a device in which one end of the ring is provided with a U-shaped notch in which the other end, which is in the form of a tongue of constant width, is inserted. Those provisions also prevent the ends of the ring from overlapping, but they do not make it possible for them to be pressed together in leaktight manner.
An object of the present invention is to propose an improved device which, while accommodating the above-mentioned constraints, effectively makes it possible to have full control over the pressing together of the two free ends of the ring, and thus guarantees leaktight contact between said two ends even if the tightening exceeds a xe2x80x9cnormalxe2x80x9d degree of tightening. An object of the invention is also to propose a device in which the ring can be manufactured simply and at low cost, even from materials other than aluminum, e.g. a relatively soft steel, optionally coated with aluminum.
The invention provides a device which comprises a sleeve suitable for being disposed around the facing ends of the two tubes, which sleeve is provided with means for reducing its diameter under the action of tightening means, the device further comprising a sealing ring suitable for being disposed inside the sleeve so as to surround the facing ends of the two tubes, said ring being constituted by a looped flat strip having first and second longitudinal ends suitable for coming into contact with each other when, with the ring being situated inside the sleeve, said sleeve is tightened around the facing ends of the tubes; the first longitudinal end being provided with a notch, while the second longitudinal end is in the form of a tongue suitable for being inserted into said notch.
The above-mentioned object is achieved by means of the facts that both the width of the tongue as measured from one side of said tongue to the other side thereof transversely to the strip, and also the width of the notch, as measured from one side of the notch to the other side thereof transversely to the strip taper in the direction going along the strip from the first longitudinal end to the second longitudinal end, that, when the tongue is in a partial insertion position in which it is inserted partially in the notch, the two sides of the tongue are suitable for coming into contact with the two sides of the notch while the free end of the tongue remains at a distance from the end wall of the notch, and that, starting from said partial insertion position, the tongue is suitable for penetrating further into the notch under the effect of the tightening.
By means of these provisions, the sides of the tongue can come into leaktight contact with the sides of the notch as soon as the partial insertion position is obtained, and said contact remains when tightening increases because the tongue can penetrate further into the notch. Thus, leaks are confined to the opening provided between the end wall of the notch and the free end of the tongue. To make the device leaktight, it is then necessary merely to take the precaution, during assembly, of placing the opening under an uninterrupted region of the sleeve, which region prevents leakage. For this purpose, the device advantageously further comprises means for defining the position of the sealing ring in the sleeve such that the longitudinal ends of the ring are angularly offset relative to a tightening opening provided in the sleeve.
Advantageously, the notch is defined laterally by two tabs that are capable of deforming by moving apart when the tongue advances into the notch from the partial insertion position. In fact, the notch may be made merely by forming a cut-out, on either side of which two tabs remain. In this particularly-simple embodiment which is entirely satisfactory, it is necessary merely to impart a width to each of the tabs that is such that they can deform plastically by moving apart as the tightening increases.